The government is drawing up new plans to tackle family breakdown that will promote any stable relationship, not just the superiority of marriage, the children's secretary, Ed Balls, reveals .

His department is due to publish a green paper on the family early in the new year, turning the issue of the promotion of families, parenting and marriage into a potential electoral battleground.

The green paper will assert that children's welfare is not necessarily best protected through marriage, but instead through "stable and lasting relationships between parents". The Conservatives are due to publish their own policy on the family shortly and have said they will recognise marriage in the tax system. Influential Tory thinkers such as Iain Duncan Smith have explicitly argued that marriage is superior to other relationships.

The green paper is expected to look at why many relationships break up around the birth of the first child, and what more can be done to bind fathers, especially younger ones, into the family at a stressful time. Currently one in three children live apart from their father by the time they reach 16.

It is also expected to include advice on parenting, the threats of the internet and what more can be done to help parents combine work and family life. Balls said: "The Tory policy is that marriage is first class and any other relationship is second class. That is fundamentally not in the interests of children. We should be about supporting strong and stable relationships."

Labour believes that the Conservative policy of recognising marriage in the tax system will prove unpopular, and stigmatises other forms of relationship, something David Cameron has tried to avoid by praising civil partnerships.

Balls said: "I think marriage is really important, but if what you know is that what makes the biggest difference is strong and stable relationships, what you cannot do is say, 'We will have a family policy which is only about marriage.' That ignores the wellbeing of relationships where there is not a marriage, either due to divorce, separation, or whatever."

Balls said the green paper would represent a shift for the Department for Children, Schools and Families. "Our job is to support parents where they want to be supported, like regulation of the internet and good schools."

He added: "We know the most vulnerable time in adult relationships is around the time of the birth of the first child; that is the point when things go wrong often, particularly for the man, particularly if they are younger … So finding ways to bind the father into the family around pre- and post-natal is really important for the strength of the relationship."

At a time of pressure on the government's Sure Start programme and childcare budgets, ministers are looking at expanding the roles of health visitors and family nurse partnerships.